Photoimageable waveguide composition and waveguide formed therefrom

ABSTRACT

Provided are photodefinable compositions suitable for use in forming an optical waveguide. The compositions include a silsesquioxane polymer having polymerized units of the formula (R 1 SiO 1.5 ) and (R 2 SiO 1.5 ), wherein R 1  and R 2  are different and are substituted or unsubstituted organic side chain groups and are free of hydroxy groups, and two or more functional end groups, and a photoactive component. The solubility of the silsesquioxane polymer is altered upon exposure to actinic radiation such that the composition is developable in an aqueous developer solution. Also provided are methods of forming an optical waveguide with the inventive compositions, optical waveguides, and electronic devices including one or more optical waveguide.

BACKGROUND OF THE INVENTION

The present invention relates generally to the field of waveguides. Inparticular, the present invention relates to photodefinable compositionssuitable for use in forming optical waveguides. The invention furtherrelates to methods of forming optical waveguides. As well, the inventionrelates to optical waveguides and to electronic devices that include anoptical waveguide.

Light is becoming increasingly important in the transmission of data andcommunications. For example, fiber optic cables have replacedconventional electrical cables in a number of applications. Opticalwaveguides typically include a core material and a cladding layersurrounding the core material. Optical radiation propagates in the corematerial and is contained by the cladding layer, which has a lower indexof refraction than the core material. Waveguides may be usedindividually or as an array supported on a substrate, and typicallytransmit optical radiation across a substrate surface. The waveguidesoften perform a passive function on the optical radiation so as tomodify the output signal from the input signal in a particular way. Forexample, splitters divide an optical signal in one waveguide into two ormore waveguides; couplers add an optical signal from two or morewaveguides into a smaller number of waveguides; and wavelength divisionmultiplexing (“WDM”) structures separate an input optical signal intospectrally discrete output waveguides, usually by employing either phasearray designs or gratings. Spectral filters, polarizers, and isolatorsmay be incorporated into the waveguide design. Waveguides mayalternatively contain active functionality, wherein the input signal isaltered by interaction with a second optical or electrical signal.Exemplary active functionality includes amplification and switching suchas with electro-optic, thermo-optic or acousto-optic devices.

Known methods of manufacturing waveguides include, for example, manuallyplacing glass fibers into hollowed out areas on a substrate; filling amold of a desired structure with a polymeric material that is thermallycured and later removed from the mold; and depositing a bulk waveguidematerial on a substrate, followed by standard photolithography andetching patterning processes using a photoresist on the bulk waveguidelayer. Each of these processes has drawbacks, however, such as requiringmultiple steps to define the waveguide, potential sidewall roughnessissues, limited resolution, and increased labor costs.

The use of photoimageable materials in forming waveguides has also beenproposed. Such materials are beneficial in that waveguides can be formedusing fewer processing steps than the above-mentioned conventionalprocesses. In developing the present invention, the use of varioushydroxybenzylsilsesquioxanes to create a photoimageable waveguide hasbeen proposed. It was thought that provision of hydroxy groups on thephenyl ring side groups would allow for development of the compositionin aqueous hydroxide solutions. From a processing standpoint, theability to use an aqueous developer solution in place of a solvent-(i.e., organic-) based developer is desirable for various reasons. Forexample, aqueous developers can be safely disposed of in anenvironmentally friendly manner and pose no health risk to those personshandling such materials, in contrast to solvent-based developers. It hassince been determined, however, that the optical loss characteristicsfor waveguides formed from the proposed hydroxybenzylsilsesquioxanematerials is higher than desired at certain wavelengths. For example,relatively high absorption at 1550 nm wave energy, one of the importantwavelengths employed in the optoelectronics industry, has been observedin such materials. The result is optical loss at that wavelength. Suchloss is believed to be due to an excessively high content of hydroxygroups in the photoimageable material.

There is thus a need in the art for compositions suitable for use inmanufacturing photoimageable optical waveguides having improved opticalloss characteristics while also maintaining developability in an aqueousdeveloper solution. As well, there is a need in the art for waveguidesformed from these compositions, for methods of forming such waveguides,and for opto-electronic devices which include such waveguides.

SUMMARY OF THE INVENTION

It has surprisingly been found that optical waveguides can be easilyprepared using the photodefinable compositions of the present invention.

In one aspect, the present invention provides a photodefinablecomposition suitable for use in forming an optical waveguide. Thecomposition includes: a silsesquioxane polymer, that includespolymerized units of the formula (R¹SiO_(1.5)) and (R²SiO_(1.5)),wherein R¹ and R² are different and are substituted or unsubstitutedorganic side chain groups and are free of hydroxy groups, and two ormore functional end groups; and a photoactive component. The solubilityof the silsesquioxane polymer is altered upon exposure to actinicradiation such that the composition is developable in an aqueousdeveloper solution.

In a second aspect, the present invention provides a photodefinablecomposition suitable for use in forming an optical waveguide. Thecomposition includes: a silsesquioxane polymer, that includespolymerized units of the formula (RSiO_(1.5)), wherein R is asubstituted or unsubstituted organic side chain group that is free ofhydroxy groups, and one or more hydroxy end groups; and a photoactivecomponent. The silsesquioxane polymer has a hydroxy content of from 0.5to 15 mole %.

In a third aspect, the present invention provides methods of forming anoptical waveguide with the inventive compositions. The methods involve:(a) depositing over a substrate a layer of the inventive photodefinablecomposition, wherein the layer has a higher refractive index than thesubstrate; (b) exposing a portion of the layer to actinic radiation; and(c) developing the exposed layer, thereby forming a core structure.

In a fourth aspect, the present invention provides optical waveguideshaving a core and a cladding. The core is formed from the inventivephotodefinable composition.

In a fifth aspect, the present invention provides electronic devicesincluding one or more of the inventive waveguides.

DETAILED DESCRIPTION OF THE INVENTION

The present invention provides photodefinable compositions suitable foruse in forming an optical waveguide. The compositions are based onsilsesquioxane polymers. Unless otherwise specified, amounts forcomponents of the composition are given in weight % based on thecomposition absent any solvent. As used herein, the term “polymer”includes oligomers, dimers, trimers, tetramers and the like, andencompasses both homopolymers and copolymers, i.e., polymers formed fromtwo or more different monomer units. The term “alkyl” refers to linear,branched and cyclic alkyl. Also as used herein, the term “developable inan aqueous developer solution” means that, in the case of anegative-working material, the composition, when (i) coated to a driedthickness of 8 μm on a silicon wafer, and (ii) then placed in a 2N NaOHdeveloper solution, a 2N KOH developer solution, or a 2N TMAH developersolution, preferably a 1N solution thereof, more preferably a 0.7Nsolution thereof, even more preferably a 0.26N solution thereof at atemperature of from 70 to 100° F. (21 to 37.8° C.) with aggressiveagitation, is completely dissolved within ten minutes, preferably withintwo minutes, even more preferably within one minute, and still morepreferably within 30 seconds. In the case of a positive-workingmaterial, this term has the same definition, except that the driedcoating would be exposed to 1000 mJ/cm² of actinic radiation between thecoating and development.

The silsesquioxane polymers useful in the present invention includepolymerized units of the formula (RSiO_(1.5)). R refers to a substitutedor unsubstituted organic side chain group that is free of hydroxygroups. It is believed that the presence of hydroxy groups on the sidechain group causes excessive optical loss at common wavelengths employedin the optoelectronics industry. Exemplary R groups include substitutedand unsubstituted alkyl and aryl groups. Such alkyl groups can bestraight chain, branched or cyclic having, for example, from 1 to 20carbon atoms, typically a straight chain or branched alkyl group havingfrom 1 to 20 carbon atoms, such as methyl, ethyl, n-propyl, isopropyl,t-butyl, t-amyl, t-octyl, decyl, dodecyl, cetyl, stearyl, cyclohexyl and2-ethylhexyl. Exemplary aryl groups include those having from 6 to 20,typically from 6 to 15, carbon atoms, such as phenyl, tolyl, 1-naphthyl,2-naphthyl and 2-phenanthryl.

The polymer can be a silsesquioxane homopolymer, in which case thepresent silsesquioxane polymers have the general formula(RSiO_(1.5))_(n), wherein R is as described above, and n is an eveninteger greater than zero. Exemplary silsesquioxane homopolymers includealkyl silsesquioxanes such as methyl silsesquioxane, ethylsilsesquioxane, propyl silsesquioxane, n-butyl silsesquioxane, iso-butylsilsesquioxane, tert-butyl silsesquioxane, and the like, and arylsilsesquioxanes such as phenyl silsesquioxane and tolyl silsesquioxane.

Alternatively, the polymer can take the form of a copolymer, either arandom- or block-type. The copolymer can be, for example, a combinationof two or more different types of silisesquioxane units, typically twoor three different types of units, with the proportions for each unitranging from 1 to 99 mole %. In a preferred aspect of the invention, thesilsesquioxane copolymer includes polymerized units of the formula(R¹SiO_(1.5)) and (R²SiO_(1.5)), wherein R¹ and R² are different and areas described above with reference to R. The copolymer can be, forexample, an alkyl/aryl silsesquioxane such as a copolymer containingmethyl silsesquioxane and phenyl silsesquioxane or containing methylsilsesquioxane, ethyl silsesquioxane, and phenyl silsesquioxane; analkyl silsesquioxane copolymer such as a copolymer containing methylsilsesquioxane and ethyl silsesquioxane; or an aryl silsesquioxanecopolymer such as a copolymer containing phenyl silsesquioxane and tolylsilsesquioxane. When more than one type of silsesquioxane units areused, it is preferred that at least one organic moiety be selected fromaryls and at least one from alkyls.

The polymer can optionally include one or more non-silsesquioxane units,in addition to the silsesquioxane units. In some circumstances, it maybe beneficial to incorporate such non-silsesquioxane polymerizable unitsinto the copolymer to achieve desired properties, for example, to impartadditional flexibility to the polymer. Such non-silsesquioxane units canbe, for example, polymerized units of the formula ((R³)₂SiO), wherein R³is a substituted or unsubstituted organic group, such as an alkyl group,for example, methyl, ethyl, propyl, and the like, or an aryl group, forexample, phenyl, tolyl, and the like. The copolymer can alternativelyinclude a single type of silsesquioxane unit as defined above, togetherwith one or more such polymerized non-silsesquioxane units.

As described above, the side chain groups of the polymer can beoptionally substituted. “Substituted” means that one or more hydrogenatoms on the side chain groups is replaced by another substituent group,for example, deuterium, halogen such as fluorine, bromine, and chlorine,(C₁-C₆)alkyl, (C₁-C₆)haloalkyl, (C₁-C₁₀)alkoxy, (C₁-C₁₀)alkylcarbonyl,(C₁-C₁₀)alkoxycarbonyl, (C₁-C₁₀)alkylcarbonyloxy, and the like.

The silsesquioxane polymers may contain a wide range of repeating units.The silsesquioxane polymers useful in the present invention may have,for example, from 5 to 150 repeating units, typically from about 10 to35 repeating units. Thus, the silsesquioxane polymer may vary widely inmolecular weight. Typically, the polymers have a weight averagemolecular weight (M_(w)) of from about 500 to 15,000, more specificallyfrom about 1000 to 10,000, even more specifically from about 1000 to5000. It has been found that the dissolution rate of the compositions inaccordance with the invention in an aqueous developer decreases with anincrease in the molecular weight M_(w) and M_(n).

The silsesquioxane polymers can further include two or more functionalend groups that allow condensation polymerization to occur. Such endgroups can be, for example, hydroxy, alkoxy such as ethoxy, propoxy,isopropoxy, carboxyester, amino, amido, epoxy, imino, carboxyacid,anhydride, olefinic, acrylic, acetal, orthoester, vinyl ether, andcombinations thereof. Of these, hydroxy groups are preferred.

The hydroxy content in the polymer is typically from about 0.5 to 15mole % based on the polymer, more specfically from about 1 to 10 mole %,even more specifically from about 2 to 5 mole %.

The silsesquioxane polymers of the present invention are typically freeof acid containing groups, such as carboxylic acid and sulfonic acidgroups. Such acid containing groups may, however, be desirable incertain circumstances.

The silsesquioxane polymer is typically present in the composition in anamount of from 1 to 99.5 wt %, more specifically from 60 to 98.5 wt %.

The described polymer materials are generally commercially available ormay be prepared by known methods. For example, a 1:1 methyl phenylsilsesquioxane copolymer can be synthesized by condensation reaction of50% methyl-triethoxy-silane and 50% phenyl-triethoxy-silane.

A photoactive component is also present in the composition to alter thesolubility of the polymer upon exposure to actinic radiation. In thecase of a negative working material, the photoactive component catalyzescoupling of exposed portions of the silsesquioxane polymer, renderingthe coupled portions insoluble in an aqueous developer. A wide varietyof photoactive components may be used in the present invention,including, but not limited to, photoacid generators and photobasegenerators. Of these, photoacid generators are preferred.

The photoacid generators useful in the present invention can be anycompound or compounds which liberate acid upon exposure to light.Suitable photoacid generators are known and include, but are not limitedto, halogenated triazines, onium salts, sulfonated esters, substitutedhydroxyimides, substituted hydroxylimines, azides, naphthoquinones suchas diazonaphthoquinones, diazo compounds, and combinations thereof.

Particularly useful halogenated triazines include, for example,halogenated alkyl triazines such as the halomethyl-s-triazines. Thes-triazine compounds are condensation reaction products of certainmethyl-halomethyl-s-triazines and certain aldehydes or aldehydederivatives. Such s-triazine compounds may be prepared according to theprocedures disclosed in U.S. Pat. No. 3,954,475 and Wakabayashi et al.,Bulletin of the Chemical Society of Japan, 42, 2924-30 (1969). Othertriazine type photoacid generators useful in the present invention aredisclosed, for example, in U.S. Pat. No. 5,366,846, the entire contentsof which are herein incorporated by reference.

Onium salts with weakly nucleophilic anions are particularly suitablefor use as photoacid generators in the present invention. Examples ofsuch anions are the halogen complex anions of divalent to heptavalentmetals or non-metals, for example, antimony, tin, iron, bismuth,aluminum, gallium, indium, titanium, zirconium, scandium, chromium,hafnium, copper, boron, phosphorus and arsenic. Examples of suitableonium salts include, but are not limited to, diazonium salts such asdiaryl-diazonium salts and onium salts of group VA and B, IIA and B andI of the Periodic Table, for example, halonium salts such as iodoniumsalts, quaternary ammonium, phosphonium and arsonium salts, sulphoniumsalts such as aromatic sulfonium salts, sulfoxonium salts or seleniumsalts. Examples of suitable onium salts are disclosed, for example, inU.S. Pat. Nos. 4,442,197; 4,603,101; and 4,624,912, the entire contentsof which patents are incorporated herein by reference. Sulfonium saltssuch as triphenylsulfonium hexafluorophosphates and mixtures thereof arepreferred.

The sulfonated esters useful as photoacid generators in the presentinvention include, for example, sulfonyloxy ketones. Suitable sulfonatedesters include, but are not limited to, benzoin tosylate, t-butylphenylalpha-(p-toluenesulfonyloxy)-acetate, 2,6-dinitrobenzyl tosylate, andt-butyl alpha-(p-toluenesulfonyloxy)-acetate. Such sulfonated esters aredisclosed, for example, in the Journal of Photopolymer Science andTechnology, vol. 4, No. 3,337-340 (1991), the entire contents of whichare incorporated herein by reference.

Substituted hydroxyimides which can be used include, for example,n-trifluoromethylsulfonyloxy-2,3-diphenylmaleimide and2-trifluoromethylbenzenesulfonyloxy-2,3-diphenylmaleimide. Suitablesubstituted hydroxylimines include, for example,2-(-nitrilo-2-methylbenzylidene)-(5-hydroxyiminobutylsulfonyl)-thiophene.Azides useful in the present invention include, for example,2,6-(4-azidobenzylidene)cyclohexanone. Naphthoquinones can include, forexample, 2,1-diazonaphthoquinone-4-sulfonate ester of2,3,4-trihydroxybenzophenone. Among the diazo compounds,1,7-bis(4-chlorosulonyl phenyl)-4-diazo-3,5-heptanedione can be used.

Photobase generators useful in the present invention can be any compoundor compounds which liberate base upon exposure to light. Suitablephotobase generators include, but are not limited to, benzyl carbamates,benzoin carbamates, O-carbamoylhydroxyamines, O-carbamoyloximes,aromatic sulfonamides, alpha-lactams, N-(2-allylethenyl)amides,arylazide compounds, N-arylformamides,4-(ortho-nitrophenyl)dihydropyridines, and combinations thereof.

The amount of photoactive component useful in the present invention, inthe case of a negative working material, is any amount sufficient tocatalyze coupling of the silsesquioxane polymer upon exposure to actinicradiation to render the coupled portion insoluble in an aqueousdeveloper. The photoactive component is typically present in thecomposition in an amount of from 0.1 to 25 wt %, more specifically from0.1 to 12 wt %.

One or more flexibilizer can optionally be included in the compositionsof the invention to impart a desired amount of flexibility to coatingsor other products formed from the compositions. It may, for example, bebeneficial to add a flexibilizer to compositions used in formingrelatively thick coatings, such as those on the order of three or moremicrons, which have an increased susceptibility to the formation ofcracks. Suitable flexibilizer materials include, for example,polysiloxanes and plasticizers such as long chain alkyds. Typically, theflexibilizer has two or more groups in its chain that are capable ofcoupling with the silsesquioxane polymer. Preferred such groups includehydroxy, alkoxy, carboxyester, amino, amido, epoxy, imino, carboxyacid,anhydride, olefinic, acrylic, acetal, orthoester, vinyl ether, andcombinations thereof. Of these groups, hydroxy is particularlypreferred. Exemplary polysiloxane flexibilizer materials includepolysiloxanes terminated with functional groups such assilanol-terminated polydiphenylsiloxanes and silanol-terminatedpolydimethylsiloxanes, typically in which the endgroups consist only offunctional groups or flexible silsesquioxane polymers, for example,those formed from reacting 33 wt % methyl-triethoxy-silane, 33 wt %phenyl-triethoxy-silane, and 33 wt % dimethyl(dialkyl)-diethoxy-silane.The flexibilizer is typically present in the composition in an amount ofless than 30 wt %, more specifically less than 20 wt %.

Other additives may optionally be present in the compositions of theinvention including, but are not limited to, surface leveling agents,wetting agents, antifoam agents, adhesion promoters, thixotropic agents,and the like. Such additives are well known in the art for coatingcompositions. The use of surface leveling agents, for examplesilicone-base oils such as SILWET L-7604 silicone-base oil availablefrom Dow Chemical Company, in the inventive compositions has been foundto provide beneficial results. It will be appreciated that more than oneadditive may be combined in the compositions of the present invention.For example, a wetting agent may be combined with a thixotropic agent.Such optional additives are commercially available from a variety ofsources. The amounts of such optional additives to be used in thepresent compositions will depend on the particular additive and desiredeffect, and are within the ability of those skilled in the art. Suchother additives are typically present in the composition in an amount ofless than 5 wt %, more specifically less than 2.5 wt %.

The compositions of the invention can optionally contain one or moreorganic cross-linking agents. Cross-linking agents include, for example,materials which link up components of the composition in athree-dimensional manner. Any aromatic or aliphatic cross-linking agentthat reacts with the silsesquioxane polymer is suitable for use in thepresent invention. Such organic cross-linking agents will cure to form apolymerized network with the silsesquioxane polymer, and reducesolubility in a developer solution. Such organic cross-linking agentsmay be monomers or polymers. It will be appreciated by those skilled inthe art that combinations of cross-linking agents may be usedsuccessfully in the present invention.

Suitable organic cross-linking agents useful in the present inventioninclude, but are not limited to: amine containing compounds, epoxycontaining materials, compounds containing at least two vinyl ethergroups, allyl substituted aromatic compounds, and combinations thereof.Preferred cross-linking agents include amine containing compounds andepoxy containing materials.

The amine containing compounds useful as cross-linking agents in thepresent invention include, but are not limited to: a melamine monomers,melamine polymers, alkylolmethyl melamines, benzoguanamine resins,benzoguanamine-formaldehyde resins, urea-formaldehyde resins,glycoluril-formaldehyde resins, and combinations thereof.

Epoxy containing materials useful as cross-linkers in the presentinvention are any organic compounds having one or more oxirane ringsthat are polymerizable by ring opening.

The compositions of the present invention may suitably comprise only asingle type of organic cross-linker, for example, only an aminecontaining cross-linker, or may contain two or more differentcross-linkers. It will be appreciated by those skilled in the art thatsuitable organic cross-linker concentrations will vary with factors suchas cross-linker reactivity and specific application of the composition.When used, the cross-linking agent(s) is typically present in thecomposition in an amount of from 0.1 to 50 wt %, more specifically from0.5 to 25 wt %, and even more specifically from 1 to 20 wt %.

The present compositions can optionally contain one or more solvents.Such solvents aid in formulating the present compositions and in coatingthe present compositions on a substrate. A wide variety of solvents maybe used. Suitable solvents include, but are not limited to, glycolethers, such as ethylene glycol monomethyl ether, propylene glycolmonomethyl ether, dipropylene glycol monomethyl ether; esters suchasmethyl cellosolve acetate, ethyl cellosolve acetate, propylene glycolmonomethyl ether acetate, dipropylene glycol monomethyl ether acetate,dibasic esters, carbonates such as propylene carbonate, γ-butyrolactone,esters such as ethyl lactate, n-amyl acetate and n-butyl acetate,alcohols such as n-propanol, iso-propanol, ketones such ascyclohexanone, methyl isobutyl ketone, diisobutyl ketone and2-heptanone, lactones such as γ-butyrolactone and ε-caprolactone, etherssuch as diphenyl ether and anisole, hydrocarbons such as mesitylene,toluene and xylene, and heterocyclic compounds such asN-methyl-2-pyrrolidone, N,N′-dimethylpropyleneurea, or mixtures thereof.

The photodefinable compositions of the present invention can be preparedby combining, in admixture, the silsesquioxane polymer, the photoactivecomponent, and other optional components in any order.

The present photodefinable compositions are particularly suitable foruse in the manufacture of optical waveguides. Optical waveguides can beused in forming opto-electrical devices including, but are not limitedto, splitters, couplers, spectral filters, polarizers, isolators,multiplexers such as wavelength division multiplexing structures,amplifiers, attenuators, switches, and the like.

The compositions in accordance with the present invention allow for thepreparation of waveguides by direct imaging. The waveguides of thepresent invention may be manufactured as individual waveguides or as anarray of waveguides. Thus, the present invention provides a method offorming an optical waveguide, including the steps of: (a) depositingover a substrate a layer of the photodefinable composition describedabove, wherein the layer has a higher refractive index than thesubstrate; (b) exposing a portion of the layer to actinic radiation; and(c) developing the exposed layer, thereby forming a core structure.

The compositions of the invention are typically first disposed as alayer on a substrate by any means including, but not limited to, screenprinting, curtain coating, roller coating, slot coating, spin coating,flood coating, electrostatic spray, spray coating, or dip coating. Whenthe compositions of the present invention are spray coated, a heatedspray gun may optionally be used. The viscosity of the composition maybe adjusted to meet the requirements for each method of application byviscosity modifiers, thixotropic agents, fillers and the like.Typically, the layer is coated to a thickness of from about 1 to 100 μm,and more specifically from about 8 to 60 μm

Any substrate suitable for supporting a waveguide may be used with thepresent compositions. Suitable substrates include, but are not limitedto, substrates used in the manufacture of electronic devices such asprinted wiring boards and integrated circuits. Particularly suitablesubstrates include laminate surfaces and copper surfaces of copper cladboards, printed wiring board inner layers and outer layers, wafers usedin the manufacture of integrated circuits such as silicon, galliumarsenide, and indium phosphide wafers, glass substrates including butnot limited to liquid crystal display (“LCD”) glass substrates,dielectric coatings, cladding layers, and the like.

The coated substrate is typically then cured, such as by baking, toremove any solvent in the coating. Such curing may take place at varioustemperatures, depending upon the particular solvent chosen. Suitabletemperatures are any that are sufficient to substantially remove anysolvent present. Typically, the curing may be at any temperature fromroom temperature (25° C.) to 170° C. Such curing typically occurs over aperiod of from 5 seconds to 30 minutes. Such curing may be affected byheating the substrate in an oven or on a hot plate.

After curing, the layer of the present composition disposed on thesubstrate is then imaged by exposure to actinic radiation. Such methodsinclude, for example, contact imaging, projection imaging, and laserdirect write imaging. The exposure pattern defines the geometry of thewaveguide, which is typically but not necessarily on the order ofcentimeters to meters in length, and microns to hundreds of microns inwidth. Following exposure, the composition can be cured, typically at atemperature of from 40° to 170° C. Curing time may vary but is generallyfrom about 30 seconds to about 1 hour. While not intending to be boundby theory, it is believed that, in the case of a negative-workingmaterial, upon exposure to actinic radiation the silsesquioxane polymercouples, rendering the exposed areas less soluble in a developersolution than the unexposed areas.

The unexposed areas may be removed, such as by contact with a suitabledeveloper, leaving only the exposed areas remaining on the substrate.The invention is advantageously developable in an aqueous developersolution. Suitable aqueous developers include, for example, alkali metalhydroxides such as sodium hydroxide and potassium hydroxide in water, aswell as tetraalkylammonium hydroxide such as tetramethylammoniumhydroxide, in water. Such developers are typically used inconcentrations from 0.1 to 2N, more specifically 0.15 to 1N, even morespecifically 0.26 to 0.7N. The developer solutions may optionallyinclude one or more known surfactants, such as polyethylene glycol,alkyl sulfonates, and other surfactants well known in the art. Thesurfactant is typically present in the developer in an amount of from0.5 to 3 wt %.

Such development may be at a variety of temperatures such as from roomtemperature to about 65° C., typically from 21 to 49° C. Developmenttime with aggressive agitation is typically within ten minutes,preferably five minutes, more preferably within two minutes, even morepreferably within one minute, and still more preferably within 30seconds.

Following development, the present waveguides may undergo a final curestep. The curing can, for example, include a flood exposure, forexample, with 1 to 2 Joules/cm² of actinic radiation. Additionally oralternatively, the waveguides may be heated at a temperature of fromabout 130° to 300° C. in air or an inert atmosphere such as nitrogen orargon.

In a preferred aspect of the invention, a waveguide is formed bydepositing core and cladding layers, wherein the cladding has a lowerindex of refraction as compared to the core. Particularly usefulwaveguides include a core having an index of refraction of from 1.4 to1.7 and a cladding having an index of refraction of from 1.3 to 1.69.

In accordance with this aspect of the invention, a first cladding layercan be deposited on the substrate prior to deposition of the core layer,and a second cladding layer can be deposited on the patterned core.Suitable compositions for the cladding material include thephotoimageable compositions described above with respect to the core, aswell as those compositions absent the photoactive component. Thus, for agiven waveguide, the same composition used in forming the core, absentthe photoactive component, can be used in forming the associatedcladding material. Typically, but not necessarily, the first and secondcladding layers can be formed from the same composition.

In forming waveguides according to this aspect of the invention, a firstcladding layer is formed on the substrate surface. This can be performedusing any of the techniques described above with reference to the corecoating. The first cladding layer can be cured, for example, thermallyor photolytically. Typically, the thermal curing temperature is from130° C. to 300° C. Such curing typically occurs over a period of fromfive seconds to one hour. Such curing may be affected by heating thesubstrate in an oven or on a hot plate. Additionally or alternatively,the waveguide can be flood exposed, for example, with 1 to 2 Joules/cm²of actinic radiation.

After curing of the first cladding layer, a core pattern is formed asdescribed above. Next, a second cladding layer is formed over the firstcladding layer and core structure. The second cladding layer may be thesame or different from the first cladding layer. However, the indices ofrefraction of the first and second cladding layers should beapproximately the same. The second cladding layer is then thermallycured and/or photo-exposed to provide a waveguide structure.

Typically, the first cladding layer is deposited to a thickness of fromabout 1 to 100 μm, more specifically from about 10 to 50 μm, and thesecond cladding layer is deposited to a thickness of from about 1 to 100μm, even more specifically from about 10 to 50 μm.

Optical waveguides of the present invention possess excellenttransparencies at a variety of wavelengths. Thus, the present opticalwaveguides may be used at, for example, 600 to 1700 nm. It will beappreciated that the present optical waveguides may be advantageouslyused at other wavelengths. Thus, the present optical waveguides areparticularly suited for use in data communications andtelecommunications applications.

Thus, the present invention further provides an optical waveguide thathas a core and a cladding, wherein the core is formed from any of theabove-described photodefinable compositions.

The waveguides of the present invention may be used in a variety ofapplications, particularly in the manufacture of opto-electronicdevices, such as in couplers, spectral filters, polarizers, isolators,multiplexers, attenuators, switches, and the like or, on a larger scale,in electronic devices such as printed wiring boards, integratedcircuits, interconnects, and the like. As used herein, the termelectronic device is intended to encompass opto-electronic devices, forexample, those described above, as well as the aforementioned largerscale devices that include an opto-electronic device.

The following examples are intended to illustrate further variousaspects of the present invention, but are not intended to limit thescope of the invention in any aspect.

EXAMPLES Example 1

50 wt % propylene glycol monomethyl ether acetate, 49 wt % phenyl-methylsilsesquioxane (50:50), 0.99 wt % triphenylsulfoniumhexafluorophosphate, and 0.01 wt % Dow SILWET L-7604 silicone-base oilare combined in admixture. The composition is spin-coated at 2000 rpmonto a six-inch silicon dioxide-coated silicon wafer and soft-baked inair on a hot plate for two minutes at 90° C., to a thickness of 8 μm.Artwork defining the required waveguide is placed directly on thecomposition. The artwork includes patterns for forming waveguides ofvarious dimensions and shapes, such as linear, branched, and curvedshaped waveguides between 2 and 14 cm in length and 5 to 15 μm inlength. 800 mJ/cm² of actinic radiation is applied to the constructionfollowed by a post-exposure-bake in air at 90° C. for two minutes. Theexposed wafer is then dipped in a 0.7N sodium hydroxide developersolution held at 37.8° C. (100° F.) for 30 seconds. The wafer is thenrinsed in de-ionized water and dried. Optical waveguides are therebyformed.

Example 2

37 wt % propylene glycol monomethyl ether acetate, 53 wt % phenyl-methylsilsesquioxane (80:20), 5 wt % triphenylsulfoniumtrifluoromethylsulphonate, 4.99 wt % polyphenylsiloxane, and 0.01 wt %Dow SILWET L-7604 silicone-base oil are combined in admixture. Thecomposition is spin-coated at 3000 rpm onto a six-inch silicondioxide-coated silicon wafer and soft-baked in air on a hot plate fortwo minutes at 90° C., to a thickness of 8 μm. Artwork as described inExample 1 is placed directly on the composition. 500 mJ/cm² of actinicradiation is applied to the construction followed by apost-exposure-bake in air at 90° C. for two minutes. The exposed waferis then dipped in a 0.7N sodium hydroxide developer solution held at 21°C. for 30 seconds. The wafer is then rinsed in de-ionized water anddried. The wafer is heated to 200° C. for 10 minutes. Optical waveguidesare thereby formed.

Example 3

37 wt % propylene glycol monomethyl ether acetate, 53 wt % phenyl-methylsilsesquioxane (50:50), 5 wt % triphenylsulfoniumtrifluoromethylsulphonate, 4.99 wt % polyphenylsiloxane, and 0.01 wt %Dow SILWET L-7604 silicone-base oil are combined in admixture. Thecomposition is spin-coated at 3000 rpm onto a six-inch silicondioxide-coated silicon wafer and soft-baked in air on a hot plate fortwo minutes at 90° C., to a thickness of 8 μm. Artwork as described inExample 1 is placed directly on the composition. The exposed wafer isthen dipped in a 0.35N sodium hydroxide developer solution held at 37.8°C. (100° F.) for 60 seconds. The wafer is then rinsed in de-ionizedwater and dried. Optical waveguides are thereby formed.

Example 4

37 wt % ethyl lactate, 53 wt % of the condensation reaction product of45 wt % phenyl-triethoxysilane, 45 wt % methyl-triethoxysilane, and 10wt % dimethyl-diethoxysilane, 5 wt % of the condensation reactionproduct of 33% phenyl-triethoxysilane, 33 wt % methyl-triethoxysilane,and 34 wt % dimethyl-diethoxysilane, 4.99 wt %2,4-bis-(trichloromethyl)-6-(4-ethoxyethoxy-1-naphthyl)-triazine, and0.01 wt % Dow SILWET L-7604 silicone-base oil are combined in admixture.The composition is spin-coated at 3000 rpm onto a six-inch LCD glasssubstrate and soft-baked in air on a hot plate for two minutes at 90°C., to a thickness of 8 μm. Artwork as described in Example 1 is placeddirectly on the composition. 800 mJ/cm² of actinic radiation is appliedto the wafer followed by a post-exposure-bake in air at 90° C. for twominutes. The exposed wafer is then dipped in a 0.26N sodium hydroxidedeveloper solution held at 37.8° C. (100° F.) for 90 seconds. The waferis then rinsed in de-ionized water and dried. Optical waveguides arethereby formed.

Example 5

37 wt % ethyl lactate, 53 wt % of the condensation reaction product of45 wt % phenyl-triethoxysilane, 45 wt % methyl-triethoxysilane, and 10wt % dimethyl-diethoxysilane, 5 wt % of polydiethoxysiloxane, 4.99 wt %triphenylsulfonium hexafluorophosphate, and 0.01 wt % Dow SILWET L-7604silicone-base oil are combined in admixture. The composition isroller-coated onto an epoxy laminate, such as commonly used in printedwiring board manufacture, to a thickness of 50 μm and dried in air in aconvection oven for 30 minutes at 90° C. The structure is annealed inair at a starting temperature of 90° C. ramped down to room temperatureat a rate of two degrees per minute. Artwork as described in Example 1,but with lines of 40 to 200 μm in width, is placed directly on thecomposition. 1000 mJ/cm² of actinic radiation is applied to theconstruction followed by a post-exposure-bake in air at 90° C. for 30minutes. The exposed structure is then dipped in a 0.7N sodium hydroxidedeveloper solution held at 37.8° C. (100° F.) for 60 seconds. Thelaminate is then rinsed in de-ionized water and dried. The resultantwaveguides are flood-exposed to 1000 mJ/cm² of actinic radiation,followed by a hard-cure at 200° C. for 60 minutes in air in a convectionoven. Optical waveguides are thereby formed.

Example 6

37 wt % propylene glycol monomethyl ether acetate, 53 wt % of thecondensation reaction product of 49 wt % phenyl-triethoxysilane, 49 wt %methyl-triethoxysilane, and 2 wt % dimethyl-diethoxysilane, 5 wt %polydiphenylsiloxane, 4.95 wt % triphenylsulfoniumtrifluoromethylsulfonate, and 0.05 wt % Dow SILWET L-7604 silicone-baseoil are combined in admixture. The composition is spin-coated at 2500rpm onto a six-inch silicon dioxide-coated silicon wafer and soft-bakedin air on a hot plate for two minutes at 90° C., to a thickness of 8 μm.Artwork as described in Example 1 is placed directly on the composition.800 mJ/cm² of actinic radiation is applied to the construction followedby a post-exposure-bake in air at 90° C. for two minutes. The exposedwafer is then dipped in a 0.7N sodium hydroxide developer solution heldat 37.8° C. (100° F.) for 60 seconds. The wafer is then rinsed inde-ionized water and dried. The wafer is heated to 200° C. in air for 10minutes on a hot plate. Optical waveguides are thereby formed.

Example 7

37 wt % propylene glycol monomethyl ether acetate, 53 wt % of thecondensation reaction product of 79 wt % phenyl-triethoxysilane, 19 wt %trifluoromethyl-triethoxysilane, and 2 wt % dimethyl-diethoxysilane, 5wt % polydiphenylsiloxane, 4.95 wt % triphenylsulfoniumhexafluorophosphate, and 0.05 wt % Dow SILWET L-7604 silicone-base oilare combined in admixture. The composition is spin-coated at 2500 rpmonto a six-inch silicon dioxide-coated silicon wafer and soft-baked inair on a hot plate for two minutes at 90° C., to a thickness of 8 μm.Artwork as described in Example 1 is placed directly on the composition.800 mJ/cm² of actinic radiation is applied to the construction followedby a post-exposure-bake in air at 90° C. for two minutes. The exposedwafer is then dipped in a 0.26N tetramethyl ammonium hydroxide developersolution held at 37.8° C. (100° F.) for 60 seconds. The wafer is thenrinsed in de-ionized water and dried. The wafer is heated to 200° C. inair for 10 minutes on a hot plate. Optical waveguides are therebyformed.

Example 8

35 wt % propylene glycol monomethyl ether acetate, 10 wt % anisole, 45wt % of the condensation reaction product of 49 wt %phenyl-triethoxysilane, 49 wt % butyl-triethoxysilane, and 2 wt %dimethyl-diethoxysilane, 5 wt % polydiethoxysiloxane, 4.95 wt %triphenylsulfonium trifluoromethylsulfonate, and 0.05 wt % Dow SILWETL-7604 silicone-base oil are combined in admixture. The composition isspin-coated at 2500 rpm onto a six-inch silicon dioxide-coated siliconwafer and soft-baked in air on a hot plate for two minutes at 90° C., toa thickness of 8 μm. Artwork as described in Example 1 is placeddirectly on the composition. 800 mJ/cm² of actinic radiation is appliedto the construction followed by a post-exposure-bake in air at 90° C.for two minutes. The exposed wafer is then dipped in a 0.7N sodiumhydroxide developer solution held at 37.8° C. (100° F.) for 60 seconds.The wafer is then rinsed in de-ionized water and dried. The wafer isheated to 200° C. in air for 10 minutes on a hot plate. Opticalwaveguides are thereby formed.

Example 9

45 wt % propylene glycol monomethyl ether acetate, 45 wt % of thecondensation reaction product of 49 wt % phenyl-triethoxysilane, 49 wt %methyl-triethoxysilane, and 2 wt % dimethyl-diethoxysilane, 5 wt %polydiphenylsiloxane, 4.95 wt % benzoin tosylate, and 0.05 wt % DowSILWET L-7604 silicone-base oil are combined in admixture. Thecomposition is spin-coated at 2500 rpm onto a six-inch silicondioxide-coated silicon wafer and soft-baked in air on a hot plate fortwo minutes at 90° C., to a thickness of 8 μm. Artwork as described inExample 1 is placed directly on the composition. 2000 mJ/cm² of actinicradiation is applied to the construction followed by apost-exposure-bake in air at 90° C. for two minutes. The exposed waferis then dipped in a 0.35N sodium hydroxide developer solution held at37.8° C. (100° F.) for 60 seconds. The wafer is then rinsed inde-ionized water and dried. The wafer is heated to 200° C. in air for 10minutes on a hot plate. Optical waveguides are thereby formed.

Example 10

37 wt % propylene glycol monomethyl ether acetate, 53 wt % of thecondensation reaction product of 49 wt % phenyl-triethoxysi lane, 49 wt% methyl-triethoxysilane, and 2 wt % dimethyl-diethoxysilane, 5 wt %polydiphenylsiloxane, 4.90 wt % triphenylsulfoniumtrifluoromethylsulfonate, 0.05 wt % Dow SILWET L-7604 silicone-base oil,and 0.05 wt % malonic acid are combined in admixture. The composition isspin-coated at 2000 rpm onto a six-inch silicon dioxide-coated siliconwafer and soft-baked in air on a hot plate for two minutes at 90° C., toa thickness of 8 μm. Artwork as described in Example 1 is placeddirectly on the composition. 800 mJ/cm² of actinic radiation is appliedto the construction followed by a post-exposure-bake in air at 90° C.for two minutes. The exposed wafer is then dipped in a 0.7N sodiumhydroxide developer solution held at 37.8° C. (100° F.) for 60 seconds.The wafer is then rinsed in de-ionized water and dried. The wafer isheated to 200° C. in air for 10 minutes on a hot plate. Opticalwaveguides are thereby formed.

Example 11

41 wt % propylene glycol monomethyl ether acetate, 41 wt % of thecondensation reaction product of 65 wt % phenyl-triethoxysilane, 33 wt %methyl-triethoxysilane, and 2 wt % dimethyl-diethoxysilane, 10 wt %hexamethylol-methane-melamine, 4 wt % polydiethoxysiloxane, 3.95 wt %triphenylsulfonium trifluoromethylsulfonate, and 0.05 wt % Dow SILWETL-7604 silicone-base oil are combined in admixture. The composition isspin-coated at 2000 rpm onto a six-inch silicon dioxide-coated siliconwafer and soft-baked in air on a hot plate for two minutes at 90° C., toa thickness of 8 μm. Artwork as described in Example 1 is placeddirectly on the composition. 800 mJ/cm² of actinic radiation is appliedto the construction followed by a post-exposure-bake in air at 90° C.for two minutes. The exposed wafer is then dipped in a 0.7N sodiumhydroxide developer solution held at 37.8° C. (100° F.) for 30 seconds.The wafer is then rinsed in de-ionized water and dried. The wafer isheated to 200° C. in air for 10 minutes on a hot plate. Opticalwaveguides are thereby formed.

Example 12

50 wt % propylene glycol monomethyl ether acetate, 49 wt % phenylsilsesquioxane, 0.99 wt % triphenylsulfonium hexafluorophosphate, and0.01 wt % Dow SILWET L-7604 silicone-base oil are combined in admixture.The composition is spin-coated at 2000 rpm onto a six-inch silicondioxide-coated silicon wafer and soft-baked in air on a hot plate fortwo minutes at 90° C., to a thickness of 8 μm. Artwork as described inExample 1 is placed directly on the composition. 800 mJ/cm² of actinicradiation is applied to the construction followed by apost-exposure-bake in air at 90° C. for two minutes. The exposed waferis then dipped in a 0.7N sodium hydroxide developer solution held at 21°C. for 60 seconds. The wafer is then rinsed in de-ionized water anddried. Optical waveguides are thereby formed.

Example 13

37 wt % propylene glycol monomethyl ether acetate, 53 wt % methylsilsesquioxane, 5 wt % triphenylsulfonium trifluoromethylsulphonate,4.99 wt % polyphenylsiloxane, and 0.01 wt % Dow SILWET L-7604silicone-base oil are combined in admixture. The composition isspin-coated at 3000 rpm onto a six-inch silicon dioxide-coated siliconwafer and soft-baked in air on a hot plate for two minutes at 90° C., toa thickness of 8 μm. Artwork as described in Example 1 is placeddirectly on the composition. 500 mJ/cm² of actinic radiation is appliedto the construction followed by a post-exposure-bake in air at 90° C.for two minutes. The exposed wafer is then dipped in a 0.26N tetramethylammonium hydroxide developer solution held at 21° C. for 60 seconds. Thewafer is then rinsed in de-ionized water and dried. The wafer is heatedto 200° C. for 10 minutes. Optical waveguides are thereby formed.

Example 14

41 wt % propylene glycol monomethyl ether acetate, 41 wt % of thecondensation reaction product of 65 wt % phenyl-triethoxysilane, 33 wt %methyl-triethoxysilane, and 2 wt % dimethyl-diethoxysilane, 10 wt %hexamethylol-methane-melamine, 4 wt % polydiethoxysiloxane, 3.95 wt %triphenylsulfonium trifluoromethylsulfonate, and 0.05 wt % Dow SILWETL-7604 silicone-base oil are combined in admixture. The composition isroller-coated onto 24 inch×36 inch (61 cm×91.4 cm) epoxy laminate, suchas is commonly used in printed wiring board manufacture, to a thicknessof 60 μm. The composition is then dried in air in a convection oven for45 minutes at 90° C. Artwork as described in Example 1, but with linewidths of 40 to 200 μm, is placed directly on the composition. 1000mJ/cm² of actinic radiation is applied to the construction, followed bya post-exposure-bake in air at 90° C. for 30 minutes. The exposedstructure is then placed into a spray developer containing 0.7N sodiumhydroxide developer solution held at 37.8° C. (100° F.) for a total of120 seconds. The laminate is rinsed in de-ionized water and dried. Theresultant waveguides are flood-exposed with 2000 mJ/cm² of actinicradiation, followed by hard cure at 180° C. for 120 minutes in air in aconvection oven. Optical waveguides are thereby formed.

Example 15

Clad (1) Layer

A first cladding layer composition is formed by combining in admixture50 wt % propylene glycol monomethyl ether acetate, 49.99 wt %phenyl-methyl silsesquioxane (50:50), and 0.01 wt % Dow SILWET L-7604silicone-base oil. The composition is spin-coated at 2000 rpm onto asix-inch silicon dioxide-coated silicon wafer and soft-baked in air on ahot plate for two minutes at 90° C., to a thickness of 7 μm. Thecomposition is then hard-baked in air on a hot plate for ten minutes at200° C.

Core

The first cladding layer is coated with a core layer and the core layeris patterned using the composition and procedures described in Example1.

Clad (2) Layer

A second cladding layer composition is formed over the patterned coreand first cladding layer using the same composition and procedures usedin forming the first cladding layer, except the thickness of the secondcladding layer after the soft-bake is 10 μm. Optical waveguides arethereby formed.

Example 16

Clad (1) Layer

A first cladding layer composition is formed by combining in admixture39 wt % propylene glycol monomethyl ether acetate, 56 wt % phenyl-methylsilsesquioxane (80:20), 4.99 wt % polyphenylsiloxane, and 0.01 wt % DowSILWET L-7604 silicone-base oil. The composition is spin-coated at 3000rpm onto a six-inch silicon dioxide-coated silicon wafer and soft-bakedin air on a hot plate for two minutes at 90° C., to a thickness of 7 μm.The composition is then hard-baked in air on a hot plate for ten minutesat 200° C.

Core

The first cladding layer is coated with a core layer and the core layeris patterned using the composition and procedures described in Example2.

Clad (2) Layer

A second cladding layer composition is formed over the patterned coreand first cladding layer using the same composition and procedures usedin forming the first cladding layer, except the thickness of the secondcladding layer after the soft-bake is 10 μm. Optical waveguides arethereby formed.

Examples 17-28

Clad (1) Layer

A first cladding layer composition is formed by combining in admixture37 wt % propylene glycol monomethyl ether acetate, 55.5 wt %phenyl-methyl silsesquioxane (50:50), 2.5 wt % triphenylsulfoniumtrifluoromethylsulphonate, 4.99 wt % polyphenylsiloxane, and 0.01 wt %Dow SILWET L-7604 silicone-base oil. The composition is spin-coated at3000 rpm onto a six-inch silicon dioxide-coated silicon wafer andsoft-baked in air on a hot plate for two minutes at 90° C., to athickness of 7 μm. The composition is blanket-exposed with 1 Joule/cm²of actinic radiation. The composition is then hard-baked in air on a hotplate for ten minutes at 200° C.

Core

The first cladding layer is coated with a core layer and the core layeris patterned using the composition and procedures described in Examples1-4 and 6-13, respectively.

Clad (2) Layer

A second cladding layer composition is formed over the patterned coreand first cladding layer using the same composition and procedures usedin forming the first cladding layer, except the thickness of the secondcladding layer after the soft-bake is 10 μm. Optical waveguides arethereby formed.

Examples 29-40

Clad (1) Layer

A first cladding layer composition is formed by combining in admixture41 wt % ethyl lactate, 56 wt % of the condensation reaction product of45 wt % phenyl-triethoxysilane, 45 wt % methyl-triethoxysilane, and 10wt % dimethyl-diethoxysilane, 2.99 wt %2,4-bis-(trichloromethyl)-6-(4-ethoxyethoxy-1-naphthyl)-triazine, and0.01 wt % Dow SILWET L-7604 silicone-base oil. The composition isspin-coated at 3000 rpm onto a six-inch glass wafer and soft-baked inair on a hot plate for two minutes at 90° C., to a thickness of 7 μm.The composition is blanket-exposed to 1 Joule/cm² of actinic radiation.The composition is then hard-baked in air on a hot plate for ten minutesat 200° C.

Core

The first cladding layer is coated with a core layer and the core layeris patterned using the composition and procedures described in Examples1-4 and 6-13, respectively.

Clad (2) Layer

A second cladding layer composition is formed over the patterned coreand first cladding layer using the same composition and procedures usedin forming the first cladding layer, except the thickness of the secondcladding layer after the soft-bake is 10 μm. Optical waveguides arethereby formed.

Examples 41-52

Clad (1) Layer

A first cladding layer composition is formed by combining in admixture39 wt % propylene glycol monomethyl ether acetate, 56 wt % phenyl-methylsilsesquioxane (80:20), 4.99 wt % polyphenylsiloxane, and 0.01 wt % DowSILWET L-7604 silicone-base oil. The composition is spin-coated at 3000rpm onto a six-inch silicon dioxide-coated silicon wafer and soft-bakedin air on a hot plate for two minutes at 90° C., to a thickness of 7 μm.The composition is then semi-hard-baked in air on a hot plate for fiveminutes at 140° C.

Core

The first cladding layer is coated with a core layer and the core layeris patterned using the composition and procedures described in Examples1-4 and 6-13, respectively, except the final hard bakes, wheredescribed, are five minutes at 140° C.

Clad (2) Layer

A second cladding layer composition is formed over the patterned coreand first cladding layer using the same composition and procedures usedin forming the first cladding layer, except the thickness of the secondcladding layer after the soft-bake is 10 μm and instead of a semi-hardbake, a full hard bake is given to the construction in air on a hotplate for 10 minutes at 200° C. Optical waveguides are thereby formed.

Examples 53-64

Clad (1) Layer

A first cladding layer composition is formed by combining in admixture37 wt % propylene glycol monomethyl ether acetate, 53 wt % of thecondensation reaction product of 49 wt % phenyl-triethoxysilane, 49 wt %methyl-triethoxysilane, and 2 wt % dimethyl-diethoxysilane, 5 wt %polydiphenylsiloxane, 4.95 wt % triphenylsulfoniumtrifluoromethylsulfonate, and 0.05 wt % Dow SILWET L-7604 silicone-baseoil are combined in. The composition is spin-coated at 3000 rpm onto asix-inch silicon dioxide-coated silicon wafer and soft-baked in air on ahot plate for two minutes at 90° C., to a thickness of 7 μm. Thecomposition is then semi-hard-baked in air on a hot plate for fiveminutes at 140° C.

Core

The first cladding layer is coated with a core layer and the core layeris patterned using the composition and procedures described in Examples1-4 and 6-13, respectively, except the final hard bakes, wheredescribed, are five minutes at 140° C.

Clad (2) Layer

A second cladding layer composition is formed over the patterned coreand first cladding layer using the same composition and procedures usedin forming the first cladding layer, except the thickness of the secondcladding layer after the soft-bake is 10 μm and instead of a semi-hardbake, a full hard bake is given to the construction in air on a hotplate for 10 minutes at 200° C. Optical waveguides are thereby formed.

While the invention has been described in detail with reference tospecific embodiments thereof, it will be apparent to one skilled in theart that various changes and modifications can be made, and equivalentsemployed, without departing from the scope of the claims.

1. A photodefinable composition suitable for use in forming an opticalwaveguide, comprising: a silsesquioxane polymer, comprising: polymerizedunits of the formula (R¹SiO_(1.5)) and (R²SiO_(1.5)), wherein R¹ and R²are different and are substituted or unsubstituted organic side chaingroups and are free of hydroxy groups; and two or more functional endgroups; and a photoactive component, wherein the solubility of thesilsesquioxane polymer is altered upon exposure to actinic radiationsuch that the composition is developable in an aqueous developersolution.
 2. A method of forming an optical waveguide, comprising: (a)depositing over a substrate a layer of the photodefinable compositionaccording to claim 1, wherein the layer has a higher refractive indexthan the substrate; (b) exposing a portion of the layer to actinicradiation; and (c) developing the exposed layer, thereby forming a corestructure.
 3. The method according to claim 2, further comprisingdepositing a cladding layer over the core structure.
 4. The methodaccording to claim 3, wherein the cladding layer comprises asilsesquioxane polymer.
 5. The method according to claim 2, wherein oneof R¹ and R² is a substituted or unsubstituted aromatic group and theother of R¹ and R² is a substituted or unsubstituted aliphatic group. 6.The method according to claim 5, wherein one of R¹ and R² is a phenylgroup and the other of R¹ and R² is a methyl group.
 7. The methodaccording to claim 2, wherein the step of developing is conducted bycontacting the exposed layer with an aqueous developer solution.
 8. Themethod according to claim 2, wherein the silsesquioxane polymer has aweight average molecular weight of from 500 to 15,000.
 9. The methodaccording to claim 2, wherein the silsesquioxane polymer furthercomprises a polymerized unit of the formula ((R³)₂SiO), wherein R³ is asubstituted or unsubstituted organic group.
 10. The method according toclaim 2, wherein the one or more functional end groups comprise one ormore hydroxy groups present in an amount of from 0.5 to 15 mole %, basedon the polymer.
 11. The method according to claim 2, wherein thephotoactive component is a photoacid generator.
 12. The method accordingto claim 2, wherein the photodefinable composition further comprises across-linking agent.
 13. The method according to claim 2, wherein thephotodefinable composition further comprises a flexibilizer.
 14. Thephotodefinable composition according to claim 1, wherein one of R¹ andR² is a substituted or unsubstituted aromatic group and the other of R¹and R² is a substituted or unsubstituted aliphatic group.
 15. Thephotodefinable composition according to claim 14, wherein one of R¹ andR² is a phenyl group and the other of R¹ and R² is a methyl group. 16.The photodefinable composition according to claim 1, wherein thesilsesquioxane polymer has a weight average molecular weight of from 500to 15,000.
 17. The photodefinable composition according to claim 1,wherein the silsesquioxane polymer further comprises a unit of theformula ((R³)₂SiO), wherein R³ is a substituted or unsubstituted organicgroup.
 18. The photodefinable composition according to claim 1, whereinthe two or more functional end groups comprise one or more hydroxygroups present in an amount of from 0.5 to 15 mole %, based on thepolymer.
 19. The photodefinable composition according to claim 1,wherein the photoactive component is a photoacid generator.
 20. Thephotodefinable composition according to claim 1, further comprising across-linking agent.
 21. The photodefinable composition according toclaim 1, further comprising a flexibilizer.
 22. An optical waveguide,comprising a core and a cladding, wherein the core is formed from thephotodefinable composition according to claim
 1. 23. An electronicdevice, comprising one or more waveguides according to claim
 22. 24. Aphotodefinable composition suitable for use in forming an opticalwaveguide, comprising: a silsesquioxane polymer, comprising: polymerizedunits of the formula (RSiO_(1.5)), wherein R is a substituted orunsubstituted organic side chain group that is free of hydroxy groups;and one or more hydroxy end groups; and a photoactive component, whereinthe silsesquioxane polymer has a hydroxy content of from 0.5 to 15 mole%.
 25. A method of forming an optical waveguide, comprising: (a)depositing over a substrate a layer of the photodefinable compositionaccording to claim 24, wherein the layer has a higher refractive indexthan the substrate; (b) exposing a portion of the layer to actinicradiation; and (c) developing the exposed layer, thereby forming a corestructure.
 26. The method according to claim 25, further comprisingdepositing a cladding layer over the core structure.
 27. The methodaccording to claim 26, wherein the cladding layer comprises asilsesquioxane polymer.
 28. The method according to claim 25, whereinthe photodefinable composition further comprises a flexibilizer.
 29. Themethod according to claim 25, wherein the step of developing isconducted by contacting the exposed layer with an aqueous developersolution.
 30. The method according to claim 25, wherein thephotodefinable composition further comprises a cross-linking agent. 31.The method according to claim 25, wherein the photoactive component is aphotoacid generator.
 32. The method according to claim 25, wherein thesilsesquioxane has a weight average molecular weight of from 500 to15,000.
 33. The method according to claim 25, wherein the silsesquioxanepolymer further comprises a polymerized unit of the formula ((R³)₂SiO),wherein R³ is a substituted or unsubstituted organic group.
 34. Thephotodefinable composition according to claim 24, wherein thephotoactive component is a photoacid generator.
 35. The photodefinablecomposition according to claim 34, further comprising a cross-linkingagent.
 36. The photodefinable composition according to claim 24, whereinthe silsesquioxane polymer has a weight average molecular weight of from500 to 15,000.
 37. The photodefinable composition according to claim 24,wherein the silsesquioxane polymer further comprises a polymerized unitof the formula ((R³)₂SiO), wherein R³ is a substituted or unsubstitutedorganic group.
 38. The photodefinable composition according to claim 24,further comprising a flexibilizer.
 39. An optical waveguide, comprisinga core and a cladding, wherein the core is formed from thephotodefinable composition according to claim
 24. 40. An electronicdevice, comprising one or more waveguides according to claim 39.